Sensor based mattress/seat for monitoring pressure, temperature and sweat concentration to prevent pressure ulcerations

ABSTRACT

A system for detecting conditions to prevent a bedsore includes a first sensor to detect a first condition that results in the bedsore and to output a first sensor signal from the first sensor indicative of the first condition that results in the bedsore, a controller to receive the first sensor signal and to determine if the condition may result in the bedsore and an alarm responsive to the controller to provide an alarm to indicate that the condition may result in the bedsore.

FIELD OF THE INVENTION

The present invention is in the field of biotechnology and relates to a method and apparatus for preventing pressure ulcerations, and more particularly, the present invention relates to a sensor system for mattress/seats and other devices which a human may come in contact with to measure pressure, temperature and sweat concentrations to prevent pressure ulcerations.

BACKGROUND

The development of sol-gel techniques for processing optical-quality thin films of silica glass has been established for various applications. One of the interesting features of the sol-gel application is that it enables one to synthesize inorganic glasses at room temperature without melting. One consideration is that the low temperature sol-gel approach circumvents the inability of the molecules to withstand the high temperatures required in the processing of oxides.

Patient immobility and debilitation are a significant health concern in the world today. This is of significant concern to patients who are suffering from a long-term illness such as trauma victims and spinal cord injury patients and who benefit from a health-care system that in some cases has lengthened and improved the quality of life. However, these patients may not able to move themselves, and consequently, these patients must rely on others for movement. A significant problem that results from this lack of mobility and that plagues these patients and consequently affects the staff of nursing homes and skilled nursing facilities is decubitus ulcers and bedsores. This complication has resulted in the death of one of the most well-known spinal cord injured patients, namely Christopher Reeve. Around-the-clock staffing for the health of the patient is available for only a minority of patients. Most patients will only have the services of a staff member for only short periods of time during the day. Because of the large and ever increasing number of patients assigned to an individual staff member, monitoring of all the needs for these patients is quite challenging. During these short periods of time that is available to each patient, the staff member may overlook the need to move these immobile patients, and the result may be decubitus ulcers or bed sores.

Each year, approximately 2,000,000 bedridden patients develop bedsores or pressure ulcers at an estimated cost of approximately $9 billion in medical expenses to treat these disorders. If vascular and diabetic ulcers are included, the cost can rise by approximately 5 times this amount. This figure does not take into account the number of days of lost productivity from the people suffering these wounds. A significant number of bed sore problems also occur in nursing homes and homes with patients confined to wheelchairs. There are approximately 1.6 million elderly and disabled people in over 17,000 nursing homes in this country alone. Of these nursing home residents, a significant percentage, approximately 13% develop bedsores every year. In 1995, the Department of Health and Human Services issued the toughest nursing home regulations in the history of the Medicare and Medicaid programs and which has led to measurable improvements in the quantity of care but have not completely eliminated the problem of bedsores. Today, there is no automatic system for monitoring pressures in bedridden and wheelchair confined patients. Consequently, patients are turned in their beds systematically and periodically to prevent bedsores.

References

-   1.     http://www.virginia.edu/topnews/textonlyarchive/September_(—)1995/W     HITAKER.txt, Jul. 12, 2002. -   2. http://www.aradvocate.com/HCFA_initiatives.html, Jul. 12, 2002. -   3. Taylor and Bader, “Sweat analysis following pressure ischaemia in     a group of debilitated subjects,” J Rehab Res Dev., 1997     July;34(3):303-8. -   4. Taylor and Bader, “The analysis of metabolites in human sweat:     analytical methods and potential application to investigation of     pressure ischaemia of soft tissues,” Ann Clin Biochem, 1994 Jan;31     (Pt 1): 18-24. -   5. Sprigle, Linden, McKenna, Davis and Riordon, “Clinical skin     temperature measurement to predict incipient pressure ulcers,” Adv     Skin Wound Care, 2001 May-Jun; 14(3):133-7. -   6. Hickerson, Slugocki, Thaker, Duncan, Bishop and Parks,     “Comparison of total body tissue interface pressure of specialized     pressure relieving mattresses,” J. Long term Eff Med Implants, 2004;     14(2);81-94. -   7. Hamanami, Tokuhira and Inoue, “Finding the optimal setting of     inflated air pressure for a multicell air cushion for wheelchair     patients with spinal cord injury, ” Acta Med Okyama, 2004 Feb;     58(1);37-44.

SUMMARY

A class of environmentally-responsive glasses has been designed to respond to different environmental stimuli. These glasses are prepared by the low temperature, solution based, sol-gel process by using organically-modified bis-[3-(trimethoxysilyl) propyl] ethylendiamine(enTMOS) precursor. Starting from the molecular precursor, the sol-gel reaction yields a solid state glass and a mechanically robust yet elastic material that is capable of generating dynamic responses when subjected to different physicochemical stimuli. These sol-gel glasses exhibit bulk changes in volume and respond to the application of different physicochemical chemical stimuli with the swelling/de-swelling being reversible, consistent and reproducible. The sol-gel undergoes a substantial change in volume when exposed to different stimuli. The change in volume is a result of the amount of liquid that is absorbed or expelled by the sol-gel. Consequently, the amount of liquid affects the electrical properties of the sol-gel. The larger the volume and correspondingly the larger amount of liquid reduce the electrical resistance of the sol-gel, increasing current. Incorporating the sol-gel into a sensor results not only in the ability to determine the presence of the stimuli but to provide a quantitative determination of the amount of stimuli present. The chemical interaction of these sol-gels with different molecules based on the charge, size and hydrophobicity/hydrophilicity can be exploited for separation of these molecules from a mixture. Typically, when the sol-gels are placed in a solution containing a mixture of different molecules, the sol-gels intake preferred species while leaving others out. This feature can be effectively used for the separation of species based on chemical structure of different molecules.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the sensor system of the present invention;

FIG. 2 illustrates the signal conditioning and data transfer unit;

FIG. 3 illustrates a central monitoring station;

FIG. 4 illustrates a chlorine sensor;

FIG. 5 illustrates a graph of the chlorine sensor;

FIG. 6 illustrates a pressure sensor:

FIG. 7 illustrates a graph of the pressure sensor.

FIG. 8 illustrates a flow chart to form the chlorine sensor;

FIG. 9 illustrates a flow chart to form electrodes;

FIG. 10 illustrates a flow chart to form the pressure sensor.

DETAILED DESCRIPTION

FIG. 1 illustrates the sensor system 100 for obtaining information from a patient and evaluating that information to determine if a bed sore is developing on the patient. Bed sores include pressure ulcerations, vascular and diabetic ulcers. The sensor system 100 includes a suite of sensors, for example FIG. 1 shows three types of sensors 109, 108, 110 which may be a chlorine sensor 108 to detect chlorine ions that are emitted from the patient, a temperature sensor 109 to detect the temperature of the patient at a location and a pressure sensor 110 to detect the pressure of the patient against a surface in order to make a determination if conditions are favorable for the development of bed sores. Chlorine, excessive pressure and temperature have been found to contribute to the development of bedsores. The specific contributions to development of bed sores of chlorine, pressure and temperature vary from patient to patient. The chlorine sensor 108 and the pressure sensor 110 may be constructed from sol-gel or from any other suitable sensor material in order to obtain information to determine if conditions are favorable for the development of bed sores. The temperature sensor 109 and the pressure sensor 110 may be constructed from liquid crystals which is an organic compound having properties that appear to be both fluid and crystalline simultaneously or may be constructed from any other suitable material. These liquid crystals behave in accordance with distinct optical properties that change when subjected to changing pressure and temperature. The color changing ability of the liquid crystals results in these liquid crystals being suitable for use for the pressure and temperature sensors 109,110. For example, liquid crystal can change in the visible color spectrum with a temperature change of 2° C. The temperature change can be expanded, and the starting point of the range can be changed. Conversely, the liquid crystals can be made to hold a particular color over a wide range of temperatures for example 10 to 60° C. Transparent liquid crystal sheets could be formed to provide the pressure and temperature sensors. Liquid crystal paint could be coated on a substrate including plastic, glass or metallic surfaces, and the resulting sheet would change their color as a function of temperature and pressure. Furthermore, pressure sensors constructed in such a manner can be calibrated to record pressure changes from zero to 500 pounds. The chlorine sensor 108, the temperature sensor 109 and the pressure sensor 110 are attached and positioned between two sheets 102, 104 and spaced apart so that the skin surface of the patient is sufficiently monitored so that no bed sores can develop. The pressure sensor 110 may have a threshold measurement of 80 g/cm² which translates to 0.011384 psi, and other thresholds may work equally well. The sheets 102, 104 may be positioned on a conventional mattress so that the patient can be monitored while lying down. Alternatively, the sheets 102, 104 may be positioned in a chair, sofa, wheelchair or any other device in which the patient may be placed and develop such conditions. The sheets 102,104 may be formed from plastic or from any other suitable material.

FIG. 1 additionally shows a connector socket 106 attached to one or both of the sheets 102, 104 for a common connection point for the wires 112 which are connected to the sensors 108,109, 110 and which are used to carry the information in the form of sensor signals from the sensors 108,109, 110. The sensors 108, 109, and 110 may communicate with the signal conditioning and data transfer unit 114 wirelessly to eliminate the connector socket 106, wires 112 and the serial connection 116 which is used to connect the connector socket 106 with a signal conditioning and data transfer unit 114.

The single conditioning and data transfer unit 114 obtains sufficient information from the patient by the chlorine sensor 108, the temperature sensor 109 and the pressure sensor 110 to determine if bed sores are developing. Other types of sensors are within the scope of the present invention in order to achieve the desired results. FIG. 1 additionally shows the sensor system 100 including a first subsystem 120 of sheets 102, 104, sensors 108, 110, 112, and signal conditioning and data transfer unit 114 and a second subsystem 122 of sheets 102, 104, sensors 108, 110, 112, and signal conditioning and data transfer unit 114. Each of the subsystems 120, 122 could be for an individual patient. The subsystems 120, 122 could be expanded to any number of subsystems and any number of individual patients. FIG. 1 shows sheets 102, 104 laid flat for use with a mattress; however, the sheets 102, 104 could be for use with a chair, a wheelchair or any other article which a patient has contact with or integral with the material.

The sheets 102, 104 are shown as rectangles which may be sized to be used with a mattress, but other sizes and shapes for the sheets 102, 104 are possible based on the needs of the patient and the device that the patient is positioned in. The sensors could be directly mounted on the patient for example while lying on the patient's back for example, while in ICU or could used with other applications such as car seats, airplane seats or other applications.

FIG. 2 illustrates a block diagram of the signal conditioning and data transfer unit 114 which includes a controller 206 to receive the sensor signals from the sensors 108, 110 and 112, and make the necessary calculations in order to determine if bed sores are developing with any of the patients being monitored and stores the sensor signals in the RAM 208. Additionally, the controller 206 receives the sensor signals from each suite of sensors 108,109, 110 of subsystems 120, 122. The controller 206 is connected to a serial connection 116 or alternatively to a wireless connection 204 to receive sensor signals from the sensors 108,109, 110. LCD display 210 is connected to the controller 206 to display the information collected and computed by the controller 206; LED display 212 is connected to controller 206 to display status information of the various hardware devices connected to the controller 206 and to provide a status indication of equipment, such as the sensors, and an alarm unit 214. The signal conditioning and data transfer unit 114 communicates with the central monitoring station 140 which includes an input output device 130 for communication and which is used to monitor other signal conditioning and data transfer units 114 at different locations. Typically, the central monitoring station 140 would be a central computer for a nursing home or a hospital or any such institution. Alternatively, the central monitoring station 140 could be shared among a group of small institutions. The input/output device 130 could include a computer keyboard and computer monitor and alternatively an antenna 304 for wireless communication or could be connected by a cable such as a USB connection 302. Like the signal conditioning and data transfer unit 114, the central monitoring station 140 includes a controller 306 to provide for calculation and control of the signal conditioning and data transfer unit 114, a RAM 308 for data storage of information, a LCD display 310 to display condition results, LED lights 312 to indicate status information and an alarm 314 to indicate when a situation develops that could harm the patient for example the development of a bed sore.

In operation, a patient is positioned between sheet 102 and sheet 104, and the chlorine sensor 108, the temperature sensor 109 and the pressure sensor 110 are positioned on one or both of the sheets 102, 104 but most likely would be located on the bottom sheet. The chlorine sensor 108, the temperature sensor 109 and the pressure sensor 110 continuously or intermittently sense the conditions of the patient and sends a sensor signal along wires 112 to the connector 106 and to the serial connector 116, and the sensor signal reaches the signal conditioner and data transfer unit 114. The signal conditioner and data transfer unit 114 receives the sensor signals from the chlorine sensor 108, the temperature sensor 109 and the pressure sensor 110.

The sensor signals are sent to RAM 208 for storage and then to the controller 206 for evaluation. If the controller 206 determines that conditions are favorable for the development of bed sores for example by determining that the one or more of the sensor signals have exceed a predetermined threshold, then the controller 206 activates the alarm 214. The predetermined threshold is stored in RAM 208 to be accessed by the controller 206 and may be stored for each of the individual patients and for each sensor 108,109,110. The controller 206 may send an alarm and/or the sensor signals to the central monitoring station 140. The controller 206 obtains data from the RAM 208 to evaluate the sensor signals sent from the chlorine sensor 108, the temperature sensor 109 and the pressure sensor 110. If the controller 206 does not for example received a sensor signal from one of the sensors, then the controller 206 activates the alarm 214 so that the defective sensor can be fixed or replaced. The LCD display 210 can display the sensor signals from the chlorine sensor 108 the temperature sensor 109 or/and the pressure sensor 110. Additionally, the LCD display 110 can display the evaluation of the sensor signals by the controller 206 so that the patient or staff member for the patient can determine if conditions favorable for bed sores are being approached. The LED display 212 can display which sensors are active and which sensors are inactive.

The signal conditioning and data transfer unit 114 transmits the sensor signals to the central monitoring station 140 through the input and output unit 130. The central monitoring station 140 may be at a physically different location than the signal conditioning and data transfer unit 114 so that the personnel at the location of the central monitoring station 140 can monitor the patient from a remote location. The signal conditioning and data transfer unit 114 can change the thresholds used by the signal conditioning and data transfer unit 114 in the comparison of the sensor signals from the chlorine sensor 108, the temperature sensor 109 and the pressure sensor 110 for the determination of favorable conditions for the development of bed sores. Consequently, the signal conditioning and data transfer unit 114 can take into account the different tolerances of different patients for favorable conditions for the development of the bed sores. Furthermore, the controller 206 can store the readings from the chlorine sensor 108, the temperature sensor 109 and the pressure sensor 110 in RAM 208 so that evaluations of the patient can be achieved based on previous history sensor readings. The chlorine ion sensor 108 as shown in FIG. 4, element 404 may be constructed using Sn-doped silica gels, and these gels respond to the presence of chlorine ions by undergoing chemical changes that can be monitored electrochemically. More particularly, when the gels are exposed to chlorine ions, the electrical properties of the Sn-doped gels change, and the resistance of the gel correspondingly changes to allow more or less current to flow through the gel. This aspect is capitalized on by forming the sensor 108 such that the sensor 108 sequesters chlorine ions from the environment of the sensor 108 as a result of the positive charge associated with the chlorine ions and the affinity of Sn for chlorine.

FIG. 5 shows the change in current with respect to the changing chloride concentration. This graph represents a substantially linear relationship, showing as the chlorine concentration increasing by powers of 10 and the current flow correspondingly increasing.

FIG. 6 illustrates additional details of the pressure sensor 110 which includes a first electrode 602 and a second electrode 604 to allow electrical connection with the pressure sensor 110. The first electrode 602 is connected to foil 606, and the second electrode 604 is connected to foil 610. The first foil 606 and the second foil 610 are formed around a layer of sol-gel 608. The compression of the sol-gel layer 608 generates an electrical potential between the first and second electrode 602, 604.

The following is a description of one method of the several methods of forming the chlorine sensor 108. The steps of this method are shown in FIG. 8. The sensor 108 includes films to form the coating on surface of the sensor 108. It should be noted that all times and concentrations may be approximate, and other methods may yield equally satisfactory results. To prepare the Sn/SiO₂ films used in the chlorine sensor 108, approximately 0.7011 gm SnCl₄ and 5H₂O is added to 750 ul of water, resulting in a concentration of 2.6 M in step 802. The precursor used in step 804 for the sol-gel coating is Tetra Methoxy Silane (TMOS), and 461 ul of TMOS is added to the mixture. The resulting concentration of TMOS in the sol is 2.56 M. The mixture is sonicated in step 804 for approximately 20 minutes in a polystyrene beaker covered with a Para film. After sonication, a homogeneous mixture is obtained. A solution of 2.5% Poly Vinyl alcohol in water (25 μl) is added in step 808 to the sol solution to prevent cracking of the gel coating.

The thin coating of the sol on the electrodes 402 is achieved with a spin coater. Here, 250 μl of the homogeneous sol is taken and applied to a circular surface of the electrode 402. The electrode 402 is placed on the spin coater, and a homogeneous thin coating is obtained by this process. All the sol-gel electrodes are left to dry under room conditions for approximately 12 hours before use. The electrodes are subsequently washed with water (50 mL) to get rid the electrodes 402 of any Cl⁻ ions.

The steps of electrode preparation are shown in FIG. 9. The sensor is constructed by depositing film in step 902 of the Sn: SiO₂ sol-gel on a 1 cm² circular polystyrene plate which is sputter coated with gold. Spin Coating technique is used to deposit the sol-gel thin films on the gold coated electrode surface. On to this film, a small Pt wire and Ag/AgCl electrode are placed using a conducting silver glue as in step 904. The working electrode has an area of approximately 1 cm² for measurements in this example. All the sol-gel electrodes are left to dry in step 906 under room conditions for approximately 12 hours before use. The electrodes are then washed in step 908 with water (50 ml) to get rid of any Cl⁻ ions.

The sensor may be calibrated by the following electrochemical measurements by which measurements could be taken in a 3-electrode configuration. The electrode is immersed in a given concentration of chloride ions and current is monitored using chromoamperometry. The saturation current is measured at 1 V applied potential or any other appropriate potential. The current is correlated with concentration of the chloride ion in the surrounding liquid.

The pressure sensor 110 can be of many types. One type of pressure sensor 110 is based on converting the pressure exerted on the pressure sensor 110 to an electrical signal which is transmitted to the signal conditioning and data transfer unit 114. Another type of pressure sensor changes color in response to the pressure being exerted on the pressure sensor 110.

With the present invention, elastic sol-gels or silicones are impregnated with conducting particles such as carbon powder or metal particles that are used to change the resistance of the sol-gel and consequently the current varies based on changes of pressure on the pressure sensor 110. These types of gels shrink or contract as pressure is applied to the pressure sensor 110, increasing the density of the conducting particles and lowering the resistance of the sol-gel.

FIG. 7 illustrates the relationship between the pressure shown as weight and the pressure signal shown as the current.

In a similar fashion as the chlorine sensor 108, the pressure sensor 110 is formed as follows as shown in FIG. 10. The conducting sol-gels are prepared by mixing 8 ml methanol with 1.4 ml of Bis[3-(trimethoxy-silyl)propyl]ethylenediamine (EnTMOS) precursor and 0.4 ml H₂O in step 1002. The mixture is sonicated in step 1004 for approximately 30 minutes to form a homogenous sol. To this sol, about 0.3 g of the conducting particles for example graphite powder, alfa aesar, synthetic, conducting grade, (˜200 mesh) is added in step 1006 to impart conductivity. The sol is then placed in a polystyrene curette to form circular disks as in step 1008 with an approximate diameter of about 1 inch and thickness ranging from 0.5 to 1 cm. The top and bottom of the gels are then connected with silver foil electrodes in a sandwich type configuration. The silver foils are connected in step 1010 to the gels by means of a conducting silver paste. Next, the sample is calibrated by the following steps. The silver foils are connected to a potentiostat for measuring current across the sample. Chromoamperometry is used to measure current at 0.5 V. The current flowing though the sample is measured as a function of weights placed on the gels. The device of the present invention can be modified to check or sense one or all of the following including pulse rate, oxygen saturation and temperature simultaneously. These sensors could use wired or wireless technology to send an activation signal to the sensor which responds to the activation signal by transmitting the sensor signal to be displayed on a screen at the nursing station. When a physician makes his/her rounds, the physician can quickly obtain the vital signs by looking on the screen.

While the above embodiments of the present invention have been described in a particular manner, one of ordinary skill in the art would recognize that substitutions and modifications would be contemplated with the teachings of the present invention. Thus, other modifications and substitutions are within the scope of the present invention. 

1) A system for detecting conditions to prevent a bedsore, comprising: a first sensor to detect a first condition that results in said bedsore and to output a first sensor signal from said first sensor indicative of said first condition that results in said bedsore; a controller to receive said first sensor signal and to determine if said condition may result in said bedsore; and an alarm responsive to said controller to provide an alarm to indicate that said condition may result in said bedsore. 2) A system for detecting conditions to prevent a bedsore as in claim 1, wherein said first sensor includes a chlorine sensor to detect the presence or absence of chlorine. 3) A system for detecting conditions to prevent a bedsore as in claim 1, wherein said system includes a second sensor to detect a second condition that results in said bedsore and to output a second sensor signal from said second sensor indicative of said second condition that results in said bedsore 4) A system for detecting conditions to prevent a bedsore as in claim 3, wherein said system includes a third sensor to detect a third condition that results in said bedsore and to output a third sensor signal from said third sensor indicative of said third condition that results in said bedsore. 5) A system for detecting conditions to prevent a bedsore as in claim 3, wherein said second sensor includes a pressure sensor to detect pressure. 6) A system for detecting conditions to prevent a bedsore as in claim 4, wherein said third sensor includes a temperature sensor to detect temperature. 7) A system for detecting conditions to prevent a bedsore as in claim 2, wherein said chlorine sensor includes a chlorine sol-gel sensor. 8) A system for detecting conditions to prevent a bedsore as in claim 5, wherein said pressure sensor includes a pressure sol-gel sensor. 9) A system for detecting conditions to prevent a bedsore as in claim 5, wherein said pressure sensor includes a pressure liquid crystal sensor. 10) A system for detecting conditions to prevent a bedsore as in claim 6, wherein said temperature sensor includes a temperature liquid crystal sensor. 11) A method for detecting conditions to prevent a bedsore, comprising the steps of: sensing to detect a first condition that results in said bedsore and to output a first sensor signal indicative of said first condition that results in said bedsore; receiving said first sensor signal and determining if said condition may result in said bedsore; and sending an alarm to indicate that said condition may result in said bedsore. 12) A method for detecting conditions to prevent a bedsore as in claim 11, wherein said sensing said first condition includes sensing to detect the presence or absence of chlorine. 13) A method for detecting conditions to prevent a bedsore as in claim 11, wherein said method includes sensing to detect a second condition that results in said bedsore and to output a second sensor signal indicative of said second condition that results in said bedsore 14) A method for detecting conditions to prevent a bedsore as in claim 13, wherein said method includes sensing to detect a third condition that results in said bedsore and to output a third sensor signal indicative of said third condition that results in said bedsore. 15) A method for detecting conditions to prevent a bedsore as in claim 13, wherein said sensing said second condition includes using a pressure sensor to detect pressure. 16) A method for detecting conditions to prevent a bedsore as in claim 14, wherein said sensing said third condition includes using a temperature sensor to detect temperature. 17) A method for detecting conditions to prevent a bedsore as in claim 12, wherein said sensing said first condition includes using a chlorine sol-gel sensor. 18) A method for detecting conditions to prevent a bedsore as in claim 15, wherein said sensing said second condition includes using a pressure sol-gel sensor. 19) A method for detecting conditions to prevent a bedsore as in claim 15, wherein said sensing said second condition includes using a pressure liquid crystal sensor. 20) A method for detecting conditions to prevent a bedsore as in claim 16, wherein said sensing said third condition includes using a temperature liquid crystal sensor. 